Technical feasibility and reliability of the Japanese disposal concept. The second progress report (H12) on research and development for geological disposal of high-level radioactive waste

The Second Progress Report (referred to as H12), documenting the progress made since the publication of the first progress report in 1992, was submitted to the Atomic Energy Commission of Japan (AEC) on 26 November 1999. The objective of H12 is to demonstrate the technical feasibility and reliability of the specified disposal concept for the high-level radioactive waste (HLW) in more rigorous and transparent manner. The report was expected to provide technical basis for the repository siting and regulatory processes as assigned by the AEC's 'Guidelines on Research and Development Relating to Geological Disposal of High-Level Radioactive Waste in Japan'. The results of research and development discussed in H12 was summarized as follows: It has been confirmed that stable geological environments are widely distributed in Japan in which an engineered barrier system constructed at depth can be expected to maintain its integrity for a long period of time, and which also function as a natural barrier to retard radionuclide migration. Work in Japan and elsewhere has provided an extensive body of data and experience which allows confidence that an appropriate repository can be designed for any suitable host rock. Following site selection, the information required to support such design work and to establish a rational site development and management plan has been outlined. The long-term safety of a repository system has been evaluated by a rigorous performance assessment methodology which includes a comprehensive evaluation of uncertainties. Despite extensive uncertainty at the present stage of the Japanese program, it has been demonstrated that a HLW repository would lead to negligible doses calculated to be below the guidelines established in other countries. (author)